Accuracy improvement technique applied to non-uniform FDTD cells using high-order implicit scheme

The finite-difference time-domain (FDTD) method is performed on discrete rectangular cells in the computational domain, and non-uniform cells are often used to save computational costs. Non-uniform cells increase the truncation error at the boundary of two domains whose cell sizes differ. We apply a high-order implicit scheme at the boundary to reduce this error. Numerical formulations and error criteria of the scheme are described and evaluated in practical applications. Compared with the conventional FDTD method, the new technique is more accurate.